THE ECONOMICS OF NEAR NET SHAPE CASTING IN NYLON 6
Producing a finished component from a near net shape, NNS, rather than a stock shape, offers economies in labor savings and material cost which increases the amount of "green backs" that drop to the bottom line. Another "green" issue positively addressed by near net shape castings is minimizing the amount of scrap generated in fabricating a finished component. Turnings carry a cost for disposal, consume storage space at the plant while waiting for scheduled pick ups, and affects the image of the plastics industry in terms of how much scrap is ultimately landfilled. NNS castings arc ideal for parts with a finished wt over 3 Ibs. Purchasing a casting to near net size minimizes the milling time necessary to create an eccentric shaped finished part For an example, fabricating an open-ended box that is 12-7/8" x 12-1/2" x 6" from a stock shape would require a block of material cut to size weighing 50 lbs. The fabrication time to mill the pocket into the box takes 13 hours per part. An investment of $850 provides the customer with a cast to near net size box weighing 27-1/2 lbs. With the pocket already cast into the shape, the fabrication time decreases to only 7 hours per part, a net saving in machining time of 6 hours per part. Using a conservative labor rate of $35.00 per hour, the customer saves $210.00 of labor cost per part. The payback on the initial investment of $850.00 is realized after machining only 4 pieces. Machining a 23" diameter multi-groove sheave (right) from a cast blank generates 100 pounds of scrap. A custom NNS casting eliminates 85% of the scrap and machine time to manufacture the same part. In addition to the dramatic and immediate saving on large milled parts, NNS castings also offer savings for turned components. The majority of bearings seem to always have a flange, and when we are talking about flanged bearings for 15" diameter shafts, material waste and turning time becomes significant. For example, 15" ID x 9" overall length bearing with a flange diameter of 23-1/2" x 3" long generates 40% material waste when turning a minor outer diameter of 18-1/2". The set up investment to make this flanged casting is $450.00. NNS casting is not only cost efficient, it is kind to the environment. A large fabricator can generate 1,000 lbs. of turnings every week. Disposing of the turnings is difficult because while recyclers are willing to take clean MoS2 filled cast nylon turnings, there is no recycling market for specialty cast nylon grades, acetal or UHMW turnings. These end up as landfill. While not entirely eliminating the amount of scrap generated, NNS castings make a large contribution in minimizing the problem and should be considered for current part requirements going through a shop. Cast Nylons Limited manufactures standard type 6 nylon shapes and near net shapes in Willoughby, Ohio. CNL also offers custom poured rod lengths and plate widths providing optimum yields for fabricators. Contact Customer Service, 800-543-3619.